The project is directed towards and understandin of the neuronal mechanisms responsible for signaling the release of hypothalamic luteinizing hormone-releasing hormone (LHRH). We will examine he relative participation and the site of action of (i) each of the two central catecholamine systems and (ii) ovarian steroid feedback action by monitoring the output (release plus tissue content) of LHRH from the hypothalamus. Besides, we will also evaluate some of the internal (monoamines, adrenals, pituitary) and external (light) factors regulating hypothalamic LHRH activity in an ovarian free environment (ovariectomized rats). In order to assess the hypothalamic output of LHRH accurately, methods for quantification of hypothalamic LHRH inactivating enzymes and for labeled amino acid incorporation into LHRH will be developed. Experimental designs encompass: transections of specific neural pathways surgically, electrical stimulation, subcutaneous implants of steroids, intracranial implants of 6-hydroxydopamine and estradiol, modification of central monoamine levels by pharmacological means and analysis of hypothalamic levels and turnover rates of monoamines.